Regulating the scavenging of free piston engines



Feb. 3, 1948. w, MQRAIN 2,435,232

REGULATING THE SCAVENGING OF FREE PISTON ENGINES Filed Nov. 10, 1945 3 Sheets-Sheet 1 lo 0 m F T NT W jI/I ll/ [1/ [if II l/j if I WILLARUAMURA N m QM,

A. MORAIN $35,232

REGULATING THE scavnneme OF FREE rrswon suemns 3 Sheets-Sheet 2 awe/whom ILL mi AMmm;

1 m w w W h m9 Filed Nov. 10, 1945 w @WN l i Feb. 3, 1948. w. A. MORMN 2,435,232

REGULATING THE SCAVENGING OF FREE PISTON ENGNES Filed Nov. 10, 1945 3 Sheets-Sheet 3 WILLARD AMURAIN;

Patented Feb. 3, l 948 UNITED. STATES PA'IQENT OFFICE REGULATING THE SCAVENGING OF FREE PISTON ENGINES Willard A. Morain, Hamilton, Ohio, assignor, by mesne assignments, to Lima-Hamilton Corporation, New York, N. Y., a corporation of Virginia Application November 10, 1945, Serial No. 627,860

, 12 Claims.

'causes erratic operation and in some instances actually stops the machine by distorting the energy balance and in any case demanding an excess fuel charge in the power cylinder. While the control of the scavenging air pressure under these conditions could be done manually, it is found more suitable and desirable to embody an adjustable automatic means therefor, such means to operate by maintaining a definite relationship between the scavenging receiver pressure and the exhaust pressure in which the scavenging pressure preferably predominates by a given amount.

The primary object of the present invention is the provision of means in connection with an engine of the free piston type to maintain automatically a proper scavenging air supply pressure for all operating conditions of the engine,

A'further object of the invention is the provision of a means and method in connection with the running of the engine whereby a minimum of power will be extracted from the working cylinder for the purpose of supplying scavenging air,

Other objects and advantages of the invention will be apparent from the following detailed description, and from the accompanying drawings illustrating three embodiments thereof, and in whichr Fig. 1 is a diagrammatical view of a free piston engine, together with an associated means for controlling the scavenging receiver pressure; Fig. 2 is a partial diagrammatical view of the same type of engine showing an alternate means of controlling scavenging receiver pressure, and Fig. 3 is a partial diagrammatical view similar to Fig. 2 illustrating still a different means of controlling the scavenging receiver pressure.

Referring to the drawings, I designates a more or less diagrammatical showing of a free piston engine, which comprises a casing 2 forming at its center a combustion chamber 3, at each of its opposite ends an air compressor cylinder 4, and at the outer end of each of such cylinders a direct bounce chamber 5. Opposed power pistons 6, 6 operate in the combustion chamber 3 and each of these attaches to an air compressor piston I in the respective cylinder 4. Each piston I has a piston 8 projecting from its outer side into the'respective bounce chamber 5. The two piston sets are connected by a suitable synchronizing means (not shown) to cause them to have opposed movements in unison, as well understood in the art. The air compressor spaces 4 are in communication through automatic valve controlled discharge ports I0 and a scavengingreceiver II. The scavenging receiver H has'a port connection l2 with one end portion of the combustion chamber 3, so that its annular cylinder end is'uncovered by the piston 6 at the end of the power or expansion stroke. A plurality of intake ports are provided around the combustion chamber 3 all of which open into the annular scavenging air connection [2 in the usual manner as shown, for example, in Fig. 3. An exhaust passage I4 is provided near the other end of the combustion chamber in position to be uncovered by its closing piston 6 near the end of its power or expansion stroke, but before the opening of the scavenging port connection l2. The compressor chambers 4 have, automatic valve controlled air admission ports 9 whereby the scavenging air may be drawn into the compressor chambers 4 during the compression stroke of the power piston G, 6 and whereby such air will be compressed in said chambers and discharged through the automatic valve controlled exhaust ports Ill into the scavenging receiver II during the power or expansion stroke of the power pistons 6, 6.

Nothing is claimed in the present application for the construction and operation of the engine itself, this being primarily the invention of Frank M. Lewis. The illustration and description thereof have, therefore, only been suiiicient for an understanding of the construction and operation of the present invention.

In the operation of free piston engines of this type, it is, as previously pointed out, diflicult to maintain balanced energy relationships between the chambers 3, 4 and 5 during reduced load operations, since the swept volume'of the air compressor chambers 4 under such operation increases slightly and the volumetric efilciency of the compressor may increase as much as 20%, and excessive load is presented to the power cylinder these conditions.

This operating difiiculty may be overcome by the provision of means that is responsive to a predetermined variance in the exhaust and scavenging pressures to reduce the scavenging pressure when the exhaust pressure is reduced, as by light load or idle running, and to increase the scavenging pressure when the exhaust pressure is increased, as under heavy loads. This control of the scavenging pressure may be effected in several ways, including directly exhausting or relieving the scavenging receiver pressure, cutting down the amount of air discharged into such receiver from the air compressor, or by-passing a portion of the compressed air as it is discharged from the haust passage M.

-quired by the air compressor piston 1.

chamber.

In Fig. 1 regulation of the said pressures is effected by opening or closing a, butterfly valve [5 located in a relief passage 16 extending from the annular scavenging port connection H to the ex- The control means for the valve includes a piston l'i operating in a cylinder lt'and having a rack-bar l9 projecting therefrom and in mesh with a quadrant 20 on the valve spindle. The scavenging relief passage i6 has a by-pass M at the inner side of the valve in connection with the cylinder chamber 22 at one side of the piston, while a by-pass 23 from the exhaust passage M has connection with the cylinder chamber 24 at the other side of the piston. A

coiled expansion spring 25 is disposed in the chamber 24 to bear against the piston and augment the exhaust pressure thereon. The spring pressure is adjusted by a screw 26 threaded through the end of the cylinder, thus making it possible to obtain a deiinite pressure relationship on opposite sides of the piston.

In the operation of this form of the inventio it will be readily seen that since the power output of the machine is represented by the volume, pressure and temperature of the exhaust gas flowing in pipe l4,'the pressure in the chamber 2d of the pressure regulating means which contains gas at exhaust pressure, under reduced load conditions, will be reduced, while that in the chamber 22, which is dependent on the scavenging receiver pressure will also reduce, but at a much slower rate, which will develop in effect a preponderance of pressure in chamber 22. This causes piston l! to move to compress the spring 25, whereby the valve I5 will be moved into a more open position. This permits escape of a part of the scavenging air around the ports of the combustion chamber 3 and through theby-pass E6 to the exhaust line [4, thus reducing to some extent the scavenging receiver pressure, The amount of air thus by-passed is in proportion to the differential pressures existing in chambers 22 and 24 of the pressure regulating cylinder 18. It is to be understood that the efiect of the spring 25 provides for the attainment of the maximum scavenging receiver pressures prior to the attainmentof the maximum exhaust receiver pressure and that said spring also provides for a complete closure of the line l6 when it is most economical for that line to be closed.

From the foregoing, it may be readily seen that under starting, idling and low load conditions, it is desirable'to by-pass a portion of the scavenging air around the working cylinder, permitting only a portion of such air to enter the combustion chamber 3 through the port connection l2, since in by-passing this air less work is re- Conversely, it is understood that as the load on the engine increases, the exhaust gas pressure in line M will increase and more air and fuel are required for the operation of the engine. To this end, the amount of scavenging air which is allowed to pass the valve l5 must be reduced so that 1a. greater percentage of the scavenging receiver air will enter the combustion chamber '3. These conditions will continue in this trend until the machine is nearing its full load output, at

which time the valve 15 will be completely closed and the entire output of the compressor chambers 4 will be forced through the combustion chamber 3 rather than around it. Since under these conditions the pressures throughout the en- 4 tire machine are at a high level, the machine continues to operate under proper pressure relationships.

In Fig. 2 the control valve l5 for the scavenging air pressure is located in the air admission line 30 of the compressor chambers t of the engine, so that the air flowing to the compressor through the intake conduit 30 and valved intake port 9 may be restricted to reduce the compressor output. Thus, although the strokes of the pistons 6, I and 8 may remain substantially constant, the scavenging air discharged by the compressor cyl-. inder 4 through the automatic valve controlled ports Hi to the receiver H, and consequently from it to the combustion chamber, will be reduced. In this form, the same as in Fig, 1, the valve has rack and pinion connection with a control piston i'l operating in a cylinder 18 with one end of the cylinder in connection with the exhaust line I4 through a branch 23 and the other end in connection with the scavenging port connection [2 through a branch I6 and with an adjusting spring 25 acting on the piston to augment the exhaust pressure. Should the engine load be increased, a proportionally greater increase in the exhaust lin pressure will occur and effect a movement to the left of the piston against the scavenging line pressure on its opposite side, thereby moving the valve It) to reduce the restriction in the inlet line 30 and permit an increase in the amount of air pumped into the scavenging receiver by-the compressor. Thus, it is again apparent that the scavenging receiver pressure will vary automatically in direct relationship to the exhaust pressure which is determined by the load.

In the form shown in Fig. 3 the control valve W is located in a compressor by-pass line 3! between the compressor outlet ports l0 and inlet ports 9. It is apparent that when such valve is open, a portion of the air discharged by the compressor is returned thereto and the scavenging receiver charge reduced a corresponding extent. The regulation of the valve l5 is effected by a predetermined differential in the scavenging receiver and exhaust pressures the same as shown and described in connection with Fig. 2.

It is apparent that in each form of the invention shown the scavenging receiver pressure varies automatically in direct relationship to the engine load whereby a minimum of power will be extracted from the working chamber for the purpose of supplying scavenging air.

I wish it understood that my invention is not limited to any specific construction, arrangement or form of the parts, as it is capable of numerous modifications and changes without departing from the spirit of the claims.

Having thus described my invention, what I claim as new, and desire to secure by United States Letters Patent, is:

1. In a free piston internal combustion engine having a combustionchamber with an'exhaust passage therefrom, and. a compressor chamber in scavenging connection with the combustion chamber, a'valve adjustable to control the pressure, in said scavenging connection, and means having connection with and operable by predetermined differential in pressure in said exhaust .passage and scavenging air connection whereby having a combustion chamber with an exhaust passage therefrom, and a compressor chamber in in scavenging connection with the combustion chamber, means havin fluid connection with both said exhaust passage and scavenging connection and responsive to a predetermined differential in pressures therein to reduce the scavenging connection pressure in predetermined relation to a reduction in the exhaust pressure, and vice versa, said means including a valve in a passage in communication with said compressor chamber together with a control for, the valve which is responsive to said differential pressures.

4. In a free piston internal combustion engine having a combustion chamber .with an exhaust passage, and an air compressor with its discharge in scavenging connection with said chamber, means including a scavenging pressure control valve having separate connection with and operable by a predetermined differential of pressures in said exhaust passage and scavenging connection to move said valve to maintain a predetermined relationship in said pressures under varying operating conditions of the engine.

5. In a free piston internal combustion engine having a combustion chamber with an exhaust passage, and an air compressor chamber having an air inlet and outlet passages with the latter in scavenging connection with the combustion chamber, a valve in connection with one of said inlet and outlet passages operable to vary the scavenging connection pressure generated by the engine, and means in separate communication with said scavenging connection and exhaust passage operable by a predetermined difl'erential in the pressure therein to move said valve to maintain a predetermined relationship in the scavenging and exhaust pressures under varying operating conditions of the engine.

6. In a free piston internal combustion engine having a combustion chamber with an exhaust passage, and an air compressor chamber with various passages in communication with the cornbustion chamber for scavenging with at least one of said passages at the inlet side of the compressor chamber and at least one at the outlet side thereof, a valve movable to close one of said passages, and means responsive to a predetermined diiferential in the scavenging and exhaust pressures of the engine to impart opening movement to the valve when the scavenging pressure predominates a predetermined extent, and

viceversa.

7. In a free piston internal combustion engine reduce the scavenging pressure when it predominates a predetermined extent, and vice versa.

,8. In a free piston internal combustion engine having a combustion chamber with an exhaust passage, an air compressor chamber with a passage in scavenging connection with said first chamber, and free pistons operating by combustion in said first chamber to compress charges in said second chamber, a valve for controlling the scavenging air pressure in said connection and means responsive to a differential in pressures in said passages to act on said valve to cause a reduction in the scavenging pressure when it predominates a predetermined extent-over the exhaust pressure, and vice versa.

9. In a free piston internal combustion engine having a combustion chamber with an exhaust passage, and an air compressor chamber with a passage in scavenging connection with said first chamber, a cylinder, a piston operatin iherein,

said cylinder'having connection at one side of the piston with said exhaust passage and. at the other side of the piston with said scavenging passage, 9. spring augmenting the exhaust presdominates a predetermined extent over the exhaving a combustion chamber with an exhaust Y haust pressure, and vice versa.

10. In a free piston internal combustion engine having a combustion chamber with an exhaust passage, and an air compressor chamber with inlet and discharge passages with the discharge passage in connection with the combustion'chamher to deliver scavenging air thereto, a. valve in said inlet passage adjustable to control the amount of air passing therethrough to the compressor chamber, and means responsive to pressures in said exhaust passage and scavenging connection to move said valve to increase the inlet passage opening when the exhaust pressure predominates a predetermined extent, and vice versa.-

11. An arrangement as called for in claim 10, together with a spring included in said means to augment the valve moving exhaust pressure action.

12. In a free piston internal combustion engine having a combustion chamber with an exhaust passage, and an air compressor chamber with inlet and outlet passages, with the outlet passage forming a scavenging connection with said combustion chamber, means forming a bypass between said inlet and outlet passages, a valve in said by-ms operable to restrict or enlarge the passage therethrough, and means responsive to pressures in said exhaust and outlet passages to move said valve to decrease the bypass opening when the 'exhaust pressure predominates a predetermined extent, and vice versa.

' WELARD A. MORAIN.

' REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,090,709 Steiner .Aug. 24, 1937 2,222,260 Janiche Nov. 19, 1940 2,303,794 Pateras Pescara Dec. 1, 1942 FOREIGN PATENTS Number Country Date France 1934 

